78 MAEIXE EEPTILES OF THE OXEOED CLAT. 



about 20 teeth on each side. Neck consisting of about 44 vertebi'Ee, the centra of 

 which in the anterior part are about as long as broad. In the shoulder-girdle tliere 

 is a well-developed interclavicle, while the clavicles are generally greatly reduced, in 

 some cases being mere films of bone adherent to the visceral face of the interclavicle ; 

 in some cases probably they are wanting entirely. Coracoids not greatly produced 

 outwards and backwards into postero-lateral processes. Pore limb a little larger than 

 the hind limb, to which it is very similar in form, the humerus not being greatly 

 expanded at its distal end even in the adult. 

 Middle Jurassic. 



The specimen upon which Prof. H. G. Seeley founded Murcenosaunis leedsi, 

 the type species of the genus, is included in the Leeds Collection (No. 25, R. 2421) ; 

 it consists of portions of the skull and mandible, 79 vertebree, some of the 

 caudals having been lost, numerous ribs, coracoids, scapulae, pubes, ischia, ilia, 

 and both the fore and hind paddles. The following account of the skeleton in this 

 genus is founded so far as possible on this specimen, but many other nearly 

 complete skeletons of the same or closely similar species have been employed to 

 supplement the description. 



Skull (PI. III. ; PI. 71. figs. 1-2 ; text-figs. 43-47).— The skull is small in proportion 

 to the size of the animal, and is roughly triangular in outline, the muzzle being bluntly 

 pointed. The upper surface of the anterior portion was probably gently convex from 

 side to side, while in the parietal region there is a high, sharp, sagittal crest, the 

 posterior end of which is the highest point of the skull, from which it slopes gradually 

 down to the tip of the snout. The following account of the individual bones is 

 founded on several more or less nearly complete example.s — the best (R. 2678) 

 belonging to the skeleton which is the type specimen of M. 'platyclis. Portions of 

 the skull of M. durobrivensis (R. 2861), as well as of the type of M. leedsi, are also 

 figured and described. 



The hasioccipital (b.oc, PI. III. figs. 1, 1 a ; text-figs. 43, 44) bears the whole of 

 the nearly hemispherical occipital condyle (oc.c), the border of which forms a sharp 

 rim, sometimes separated by a short neck from another parallel rim (text-fig. 44) ; 

 the upper border of the condyle in some specimens is a little flattened beneath the 

 neural canal ; there is no pit marking the original position of the notochord, 

 such as has been described as occurring on the occipital condyle of Ojjhtha hnosaurus 

 (see supra, p. 6). The upper surface of the bone (text-fig. 43, B) bears a pair 

 of large elongated oval facets (exo.f.), for union with . the ventral end of the 

 exoccipitals and opisthotics ; the space between these facets {7i.e.), forming the 

 floor of the brain-case, is narrow and concave from side to side behind, while in 

 front it widens out and bears in its middle line a strong longitudinal ridge which 

 in some specimens is paired. The anterior face of the bone (text-fig. 43, C) is nearly 

 vertically truncated by the surface [is.f.) for union with the basisphenoid. Anteio- 



